(1) Heat Detection (observing “estrus”)
The “best” sign is
the mounting of the animal in heat. She
stands still for others to mount her.
Then our timing of insemination is easier, as you have standing heats
for reference. Breed cows standing at
night the following morning, breed cows standing at morning after lunch, or if
still heated up, wait to evening.
(The idea is to service at the end of standing heat—more on that later).
A beginning sign
of estrus onset is the swelling of the vulva and the release of cervical mucus,
which is shiny and clear. The cow will
be more active, restless, perhaps bawling a bit. As the estrus progresses, the cow may try to
mount other cows to draw attention.
Finally you see her standing to be mounted.
The stages of
standing heat last several hours, so will be mixed in with feeding and other
routines. At the end of heat, cows
start to refuse to be mounted (AI should occur right away, if not
already). The next day the cow will be
quiet again—and within another day, you will likely see blood on the tail.
If not serviced,
or if conception does not occur, you can expect her next cycle between 17 and
24 days later (21 days is the usual interval). “False” heat signs are often seen mid
cycle (ie, 9-11 days after a true heat) and are just a result of the hormonal
production that stimulates the complete cycle.
(2) Semen Handling (protecting conception)
Your object in
semen handling is to preserve unused semen by equipment and procedures that
optimize the number of live sperm available in the straw after it is thawed for
use.
Your liquid
nitrogen semen tank is designed to maintain semen in a full state of suspended
animation. Cryogenic temperatures (-320 F in the liquid, -140 F in the vapor)
are adequate to maintain that state, but any time the semen straws/canes are
moving above the vapor line in the neck of the tank (or between tanks)
molecular movement from warming can begin.
Transfer of semen
canes should occur within a ten second interval. A similar eight second time limit is “the
rule” on removing the straw you are ready to thaw for breeding—to protect the
straws you are NOT ready to use. (If
you do not get the straw you want in eight seconds, put the cane and canister
back in the bottom of the tank, let it cool down 30 seconds, then lift it up
and try again.)
We find the
canister in which the sire we wish to use is stored. You can hold the canister within the neck of
your tank, by light pressure on the fiberglas stem, with the same hand that
holds the cane steady (with thumb and forefinger) while you remove a
straw. Then (1) drop the cane down
into the canister, (2) drop the canister into the neck, (3) put the removed
straw in your thaw water, (4) set the canister in its hanger, (5) plug the tank
neck. The removed straw is being
thawed, it is of secondary importance to the straws returning to the safety of
your semen tank—thus the logic of the order given above.
Why thaw in warm
water?? Because it is likely the semen
you have was collected at multiple locations and with different extenders
(fluids added to protect the sperm cells through freezing and thawing). It is known that “pocket thaw” seems to work
with milk extender semen, but can damage egg yolk, citrate, and soybean oil
extended semen. But warm water thaw
works equally with ALL semen straws.
(3) The AI technique (rectal palpation, cervical
fixation)
The thawed straw
will be wiped dry, inserted into the barrel of a warmed AI gun. The end of the straw is cut open, a sterile
sheath is drawn over it (and secured by o-ring or spiral at the shank of the
gun). A dry paper towel is wrapped over
the end, to reduce temperature shock, and slipped into your vest.
You will slide an
OB glove over your left arm, fitting the hand to your fingers. You will apply OB lube to the palm of your glove,
and (if a soap lube, make a suds to clean the vulva surface) wipe lubricant on
the vulva lips, then enter the rectum one finger at a time to relax and dilate
the anus. Any manure she pushes back to
you, should be allowed to flow out, thus keeping the rectal rings in motion
(more on that later). Once the
manuring stops, with your right hand, take an unfolded towel in the flat of
your hand and make a single comprehensive wipe across the vulva surface, to clean
the area for entry.
Taking the AI gun
in your right hand, you now enter the vulva using a slightly uphill angle (to
avoid an entry into the urethra, which drains the bladder—an area very
sensitive to the cow and unconnected to her reproductive system). You will find that pushing gently down
against the vulva from inside with your left hand (folded into a fist)
usually will spread the vulva lips apart to make a cleaner entry.
I then relax my
left arm inside the rectum, while sliding the AI gun as far into the vagina as
it will go easily. In most cases (as the vagina is a funnel and
only leads to the cervix) the gun will end up at a point in front of or
slightly alongside the cervix. I then
work my left hand down to find the end of the gun and explore the tissue
structures it has found, to detect the size, shape and angle of the cervix.
Keep in mind the
entire reproductive tract—vagina, cervix, uterus body, uterine horns, and
ovaries—are mounted on a membrane that is anchored to the pelvic bones,
designed to allow stretching of the weight of the calf into the body cavity as
pregnancy progresses. So the cervix
and uterus can move about, and we must be careful not to “bulldoze” what we are
seeking over the edge of the pelvis into the body.
The cervix can be
grasped roughly half around by lifting it off the membrane, and this allows you
some control of cervix movement as you seek to guide the gun into its vaginal
entrance. The cervix feels like a
“chicken neck”—you may sense folds (rings) that the gun passes through to reach
the uterine body.
Once you pass the
gun through the cervix, you will feel the tip coming out of the cervix. You need to hold the gun in the uterine
body, by placing your index finger over the tip, so it does not slide up into
one of the uterine horns. At this
point, you grasp the plunger with your right hand, push the semen into the cow,
then remove the gun, and finally remove your left arm.
Once your gloved
hand is out of the cow, grasp the base of the vulva between thumb and finger,
and as soon as you find the clitoris (buried in the fat tissue of the vulva
base), flick it repeatedly. If done
with finesse and sensitivity, the cow will arch her back—at this point, her
nervous system has been sent the signal that breeding has taken place, and will
then initiate the steps to trigger ovulation.
(4)
How conception actually occurs
Six to twelve
hours after the end of standing heat (when you bred the cow), the follicle on
one ovary will rupture and release its ovum (egg). The infindibulum membrane catches it, and
sends it up the fallopian tube, where it will meet the waiting sperm
cells. Sperm rub against the enzyme
shell until one is able to penetrate and complete conception. Over the next week, during cell division,
it migrates to the horn and will attach to the uterine wall. Over the next six weeks, it transitions to
full fetal attachment.
The miracle of
life—celebrated each spring with the birth of calves
Nothing beats the sight of a
herd of momma cows in green paddocks, grazing grass and nursing a full crop of
calves. The cattleman knows reward
for the prior season’s time and expense for breeding those cows, and can
predict his likely income.
But that means we need to be
picking out sires, ordering semen, restocking our supplies and preparing for
heat detection, maybe estrus synchronization, and breeding.
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